1. Field of the Invention
The present invention relates to a method of numerical-control scraping of a work piece, and more particularly to a method that can scrape a three-dimensional surface of the work piece accurately.
2. Description of Related Art
In general, a conventional hard rail for a machine tool needs to be scraped before assembling, and a scraping process is used to scrape relative high points of a contacting surface of the conventional hard rail. The scraping process can form multiple recesses on the contacting surfaces of the conventional hard rail. The recesses can be used to store lubricant to lubricate movement of a moving element on the conventional hard rail and this can reduce the friction force between the moving element and the conventional hard rail. Therefore, detecting a surface roughness of the scraped surface is very important to maintain functions of the conventional hard rail, since the surface roughness may affect mobility of the moving element on the conventional hard rail.
A conventional method for determining the surface roughness of the scraped surface comprises the following steps: painting ink on the surface of a standard holder, sliding a work piece on the surface of the standard holder so ink will be removed and be found on high points of a scraped surface of the work piece, scraping the high points of the work piece and measuring differences of height of the high points of the work piece with a measuring tool. The above-mentioned steps are repeated until the differences of height of the high points of the work piece reach the requirement. When the differences of height of the high points of the work piece reach the requirement, multiple recesses are averagely formed on the scraped surface of the work piece, sliding the work piece on the surface of the standard holder so ink will be removed and be found on the scraped surface of the work piece and a charge-couple device (CCD) can be used to screen the inked-and-scraped surface of the work piece to analyze the surface roughness of the work piece to detect the uniformity of the high points distribution of the scraped surface of the work piece.
Though the conventional detecting and scraping method can be used on a work piece of the hard rail, the detecting result of the described conventional method is not precise since the results of the conventional method are easily affected by human error and cannot analyze the work piece accurately.
To overcome the shortcomings, the present invention provides a method of numerical-control scraping of a work piece to mitigate or obviate the aforementioned problems.